1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, it relates to a pressure-connection type semiconductor device such as a thryristor or a high-power transistor.
2. Description of the Background Art
Japanese Patent Laying-Open Gazette No. 79669/1987 discloses a conventional semiconductor device of this type. FIG. 1 is a sectional view showing the semiconductor device according to this prior art example.
Referring to FIG. 1, a thyristor element 1 is provided in the form of a disc, while a gate electrode 1b and a cathode electrode 1c are provided on the lower surface of a semiconductor substrate 1a in inner and outer peripheral regions, respectively. An anode electrode 1d is provided on the upper surface of the semiconductor substrate 1a. A doughnut-shaped temperature compensator 2 is pressed on the cathode electrode 1c to be electrically in contact with only that. An external cathode electrode 3 is pressed on the temperature compensator 2 to be electrically in contact with only that. Further, a discoidal external anode electrode 4 is pressed on the anode electrode 1d to be electrically in contact with only that. A flange 5a is provided on the outer peripheral region of the external cathode electrode 3, while a flange 5b is provided on the outer peripheral region of the external anode electrode 4. An insulating sleeve 6 couples these flanges 5a and 5b with each other, to thereby integrally couple the external cathode electrode 3 with the external anode electrode 4 while maintaining an electrically insulated state.
A disc spring 7 and an insulator 8, the configuration of which is shown in FIG. 2, are received in this order in a cavity 3a defined in a central portion of the external cathode electrode 3. A gate lead 10 is inserted in a through hole 8a defined in an upper central portion of the insulator 8 and an insulating tube 9, so that the first end of the gate lead 10 is press on the gate electrode 1b to be electrically in contact with that by spring force of the disc spring 7 through the insulator 8, while the second end thereof is electrically connected with a gate terminal 11.
Assembly sequence of the semiconductor device shown in FIG. 1 is as follows: First, the gate lead 10 is inserted in the through hole 8a of the insulator 8 and the insulating tube 9, to thereby form an assembly A. Then the disc spring 7 and the assembly A are introduced in this order into the cavity 3a of the external cathode electrode 3, and the temperature compensator 2 is placed on the upper surface of the external cathode electrode 3. Further, the thyristor element 1 is so arranged that the temperature compensator 2 faces the cathode electrode 1c and that an end of the gate lead 10 faces the gate electrode 1b. Finally, the external anode electrode 4 is placed on the anode electrode 1d of the thyristor element 1, and the flanges 5a and 5b are coupled with each other by the insulating sleeve 6 with externally applying pressure to the external cathode electrode 3 and the external anode electrode 4.
FIG. 3 illustrates positional relation between the temperature compensator 2, the external cathode electrode 3, the insulator 8 and the gate lead 10. As shown in FIG. 3, a clearance is defined between the insulator 8 and the gate lead 10 since the bore diameter a of the through hole 8a of the insulator 8 is larger than the outer diameter b of the gate lead 10, whereby misregistration may be caused between the insulator 8 and the gate lead 10. Similarly to the above, another clearance is defined between the insulator 8 and the external cathode electrode 3 since the inner diameter c of the cavity 3a of the external cathode electrode 3 is larger than the outer diameter d of the insulator 8, whereby misregistration may be caused between the external cathode electrode 3 and the insulator 8. Further, still another clearance is defined between the temperature compensator 2 and the insulator 8 since the inner diameter e of a through hole 2a provided in the central portion of the temperature compensator 2 is larger than the outer diameter d of the insulator 8, whereby misregistration may be caused between the temperature compensator 2 and the insulator 8. In other words, the conventional semiconductor has no function of relatively locating the temperature compensator 2, the external cathode electrode 3, the insulator 8 and the gate lead 10. Thus, misregistration may be caused between these elements. When the temperature compensator 2, the external cathode electrode 3, the insulator 8 and the gate lead 10 are dislocated as shown in FIG. 4, for example, the lower surface of the gate electrode 1b (FIG. 1) cannot correctly face the first end of the gate lead 10, while the lower face of the cathode electrode 1c (FIG. 1) cannot correctly face the upper surface of the temperature compensator 2, to thereby disable correct pattern alignment.
Similar problems are also caused in a statict induction thyristor, a gate turn-off thyristor, a high-power transistor and the like. Particularly in such devices, improvement in degree of integration and increase in bore diameter of semiconductor elements, which have been required in recent years, are difficult to attain if the aforementioned clearances are defined. With improvement in degree of integration and increase in bore diameter of the semiconductor elements, numbers of gate electrodes etc. provided on the semiconductor elements are increased to, so that the number of portions requiring alignment are also increased, whereas it is difficult to correctly align all of such portions.